Tension and compression spring device linear motion control device

ABSTRACT

A spring device which operates in tension to be used in attenuating shock loads in a flexible tension element, which can be used, for example, on the mooring rope of a floating vessel. Also a spring device acting in compression which can serve as shock attenuating standoff for use, say, in holding a floating vessel away from contact with a mooring structure. Also, a device to provide slack or give in a mooring rope to allow a moored floating vessel to freely rise and fall with varying water levels such as caused by tides. 
     Secondly, a device, which by virtue of its shape, creates a retarding force when slid along a flexible tension element, such as a rope. This force is easily modulated by varying the tension in the element. A possible use would be to control, from below, the rate of descent of an object being lowered down a rope.

BACKGROUND OF THE INVENTION

It is commonplace to moor a floating vessel to a fixed object such as a dock or to another floating vessel. Wave, wind and tidal current action can affect moored vessels so as to cause damage to the vessel(s) and/or dock and so as to make living and sleeping aboard very uncomfortable.

Accordingly, there is extensive prior art to relating to devices that control the motion of a floating vessel while moored. Many of them are complex, cumbersome and costly to manufacture or are simply bumpers which can scuff the vessel causing minor but unsightly damage to the vessel.

The device disclosed in U.S. Pat. No. 7,089,877 B 1 is an example. While functioning in both tension and compression, it is complex and cumbersome to use. U.S. Pat. No. 5,803,439 reveals a device which functions only in tension and too is quite complex. U.S. Pat. No. 3,817,507 shows a simple device but will work only in tension.

There are other applications for this device. One use would be to damped shock loads in a rope, chain, or cable used in towing on object such as a car or water skier. Another use would be maintain tension in ropes, chains, or cables used in lashing down cargo loads, or holding down a tent.

This device, in another embodiment, can also be used by mountain climbers or rescue personnel to lower themselves or other objects along the climbing rope. The rate of descent is controlled by the amount of tensioned maintained in the tail end of the rope. This can be accomplished by the occupant, say, or by a person below at the end of the rope.

There are numerous other devices that will accomplish this that were revealed in the patent search and in a search of commercially available gear. U.S. Pat. No. 4,588,045 reveals a device which can perform the same function as claimed for this device but it is limited to use of a flat strap as a tension element. The device shown in U.S. Pat. No. 6,959,783 is designed to function using a rope as a tension element. In U.S. Pat. No. 7,237,651 the shown device may function using several kinds of tension elements but the device is very complex.

This invention embodies a device that is very simple and easy to manufacture. It is superior by virtue of the large internal friction which allows it to be used with many types of flexible tension elements, such as rope, chain, wire, cable etc.

SUMMARY OF THE INVENTION

The object of this invention is to provide a simple device which can attenuate shock loads in a flexible tension member and at the same time act as a resilient device acting in compression to keep objects connected by a flexible tension member from contacting each other.

A hollow resilient tube, made from a material such as, but not limited to, rigid PVC is manufactured in such a way as to encompass one or more bends. The two ends of the tube are aligned in such a way as to point diametrically away from each other. A rope then passed through tube will tend to straighten the resilient tube when tension is applied to it. This springy deformation of the tube causes an attenuation of any shock loads placed on the rope.

If the two ends of the tube are made sufficiently long enough, they can be butted against the attachment fixtures to which the ends of the rope are fastened, thus keeping the connected objects separated and shock loads between the objects are attenuated in both tension and compression.

The preferred embodiment of this invention is an “S” shaped tube made from rigid PVC through which the rope is passed. The ends of the tube are made to a length required to keep the connected objects separate. Also, the ends of the tube are rolled back “turtleneck” style to present a rounded edge to the rope in order to prevent chafing.

Another embodiment of the invention is a tube formed in the shape of one or more circular coils. The ends of the tube again face in opposing directions and the rope feeds in one end and ultimately comes out the other. The resilience of the coil(s) again creates a springiness in both tension and compression.

Of the two embodiments mentioned, this one is suited to the mountain climber lowering himself down his climbing rope. The rope is fed through the tube and the climber harnesses himself to the coil. The internal friction of the rope in the coil retards his descent, the rate of which is controlled by how much tension the climber maintains in the tail end of the rope.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 & 2 show two of many possible embodiments of the invention;

FIG. 3 shows a cut-away view of an end of the invention;

FIG. 4 shows the invention in two embodiments used in tension and compression in mooring a boat; and

FIG. 5 shows the invention in one embodiment used in lowering a load along a rope.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the preferred embodiment of the invention 1 for mooring, towing, and tie-down purposes. The upper end of the invention 1 is shown cut-away to reveal on of the curled over ends 9 to prevent chafing of the rope 2, which is fed through the tube 1.

FIG. 2 shows another embodiment of the invention 3, with a rope 2 passing through it. The curled over ends are not shown.

FIG. 3 shows a cut-away view of one of the ends 9 of the invention 1 & 3. The curled over edge presents a rounded surface to the rope to prevent chafing.

FIG. 4 reveals a boat 5 moored to a dock 4 with the use of four ropes or lines 2. The ropes 2 are attached to four cleats 6 on the dock 4. The other ends of the ropes 2 are attached to two bow cleats 10 and one stern cleat 11. The two ropes at the bow of the boat 5, which restrain the bow in a port to starboard direction are run through the “S” embodiment 1 of the invention. These “S” embodiments 1 are made short enough so as not to butt against dock cleats 6 and bow cleats 10. Thus the “S” embodiments 1 shown at the bow act only in tension to attenuate shock loads in the bow ropes 2 caused by wave, wind, and tidal action.

The stern of the boat 5 is restrained at the port side by one rope 2 which is run through a “coil” embodiment 3 of the invention and attached between dock cleat 6 and stern cleat 11. The ends of the “coil” embodiment 3 are made long enough so as to butt against both dock cleat 6 and stern cleat 11. This allows the “coil” embodiment 3 to act in both tension and compression to attenuate shock loads in the stern rope 2 caused by wave, wind, and tidal action.

FIG. 5 demonstrates the “coil” embodiment 3 of the invention being used as a linear motion control device. Rope 2, attached to an elevated structure 12 is strung through the “coil” embodiment 3 of the invention and the free end of the rope 2 is in the hands of a person 8 on the ground. To lower a load 7, in this case a bucket, from an elevated position to the ground, the load 7 is tied to the “coil” embodiment 3 of the invention. The person on the ground 8 then controls the downward motion of the load 7 by varying the tension in the rope 2. This acts to modulate the friction created by the “coil” embodiment 3 of the invention and load 7 sliding down the rope 2 and allows for control of the rate of descent of the load 7. 

1. A spring device which consists of curved hollow resilient tube or pipe which encases a flexible tension element, be it a rope, chain, cable, or wire etc. in which shock loads need to be controlled. When a load is placed on the tension element the curved flexible tube will tend to straighten and in the process absorb or attenuate any shock loads placed on the tension member.
 2. A device as claimed in claim 1, to maintain tension in a flexible tension element.
 3. A device as claimed in claim 1, when manufactured to a length so as to butt against the attachment points of a flexible tension element, which acts not only in tension but also in compression to attenuate shock loads in the attaching element between the attachment points.
 4. A device as claimed in claim 1, with the exception that the tube need not be resilient, which by virtue of its shape, creates a retarding force when slid along a flexible tension element, such as a rope. This force is easily modulated by varying the tension in the element, thus controlling the motion along the tension element of the device and any load placed on it. 